12. Carbohydrates: Flashcards
Classification of carbohydrates:
digestible- non digestible classification is based on carbohydrates units Glucose 1 MONOSACCHARADIS sucrose 2 OLIGOSACCARIDES starch many POLYSACCHARIDES
Main carbohydrates in food:
glucose, fructose, sucrose, lactose, starch
Metabolism of carbohydrates:
digestion and absorption in the small intestine (glucose, fructose and starch that is break down by pancreatic amylase become monosaccharides)
fragmentation in the large intestine (lacotse, fructose, fermented by gut flora transformed into volatile fatty acids)
Sugar transporters on enterocytes:
Glucose and galactose transported by sodium-glucose transport protein
fructose is absorbed via facilitated transprt GLUT5
all three transported in the bloos by GLUT2
Carbohydrate malabsorption:
- lactose intolerance
- glucose-galactose malabsorption syndrome
- fructose malabsorption
Requirments carbohydrate:
brain needs 120 g glucose/d
pregnant and lactant lady: 175-210
body can produce glucose from protein and fat
Carbohyrate storage:
Glycogen in the liver 100-120g
glycogen in skletal muscle (420 g)
when no more storage, glucose must come from diet or via gluconeogeesis
Regulation of blood glucose concentration:
Pancreas secrete insulin, secrete glucagon
What is diabetes mallitus?
Type 1 diabetes:
autoimmune destruction of pancreatic cells
not enough insulin is secreted
Type 2 diabetes:
Insulin resistence:
cellular insulin receptor not so sensitve
more insulin secretionrequired for same effect
less glucose homeostasis
Elevate insulin level cause:
Hyperinsulinaemia
basal insulin concentration increase with age
associated with obesity and low physical activity
What prevention of type 2 diabetes:
Decrease risk:
dairy products, whole grains, coffee, tea
Increased risk:
fruit juice, red meat, white rice, french fries
Physical activity is very important!!!
Meal blood glucose response:
Test to help compare foods after increase of blood sugar after a meal
Limitation of GI measurments:
amount of available carbohydrates very different in different products
inter-individual variation in glycemic response
Factors influencing postprandial glucose response:
Type of starch
cooking or food processing
interaction with other nutrients
Factor influencing digestibility of starch:
granular size crystalline structures (A,B,C )
Interaction with starch an other nutrients:
granules can be enclosed in a protein matrix (pasta)
Resistent starch:
physically inaccessible starch in whole grains
raw starch granules
retrograded starch
Starch gelatization and retrogradation:
starch undergos swelling when heated in water, retrogradation when amylose and amylopectinechains realign
crystalline structures are formed after cooling
Dietary fiber:
Intrinsic plant cell wall polysaccharides
Edible parts of plants that are resistent to digestion and absorption in the small intestine
Include polysaccharides, lignin, plant
Promote beneficial effect like laxation, blood cholesterol attenuation glucose attenution
main components of dietary fibre:
Xylan dietary fibers that not digested promote other factors: low glucose and cholesterol resistence to CVD and colon cancer OAT b-GLUCAN
Fermentaition in the colon
solube dietary fibre:
extensive fermentation by microflora in colon
formation of gases: high
growth of gut bacteria: high
Insoluble dietary fibre:
Minimal fermentation low gases and low gut bacteria
Probiotics and prebiotics
Probiotica: living bacteria
prebiotics: non digestible food ingredietns that affect and stimulate growth and activity of bacteria
Role of dietary fibre in colorectal cancerogenesis:
dietary fibre protect by modyfing colonic bacterial flora
being fermented create good environment less conductive to bacterial production of cancirogens
sppeding the rate of transit of colonic contents
Low carbohydrate for lose weight?
keton bodies fuels for brain, muscle, heart
degradation of muscle proteins
unbalanced elecrolyte status
It takes a lot of carbo to promote lipogenesis
